A prospective, correlational, repeated measures design will be used to evaluate the immune status of trauma patients. A combination of assays including serial assessment of serum complement C3 level, measurement of delayed type hypersensitivity skin response, and the differentiation of immune cell functional profile through the characterization of immune cell phenotypic responses to stimuli will be performed on patients sustaining moderate to severe injury. The specific aim of the study is to determine if early measurement of an immune cell functional profile is as effective as the measurement of delayed type hypersensitivity skin response or the measurement of serum complement C3 level in predicting the progression to systemic inflammatory response syndrome. The GCRC will be used to assist with the collection of the blood specimen tubes from 911 trauma patients.